The central objective of this research is to define ways in which drugs interfere with cholinergic systems on subcellular, cellular and system levels, using gas chromatography/mass spectrometry in conjunction with both stable and radioactive isotopic labelling to obtain a dynamic assessment of cholinergic processes and the factors controlling them. Acetylcholine and choline turnover in specific brain regions will be assessed using several approaches, including the rate of incorporation of labelled precursors, the rate of accumulation after pulse administration of an anticholinesterase, the properties of synaptosomes isolated from brain regions after various treatments and the rates of release of acetylcholine and choline from in vitro preparations and surfaces of the brain. Generation of choline by brain tissue will be investigated as a possible regulatory process in acetylcholine metabolism. The influence of electrolytic lesions at remote sites on turnover and release will also be studied. These methods will be used to define the effects of drugs on cholinergic systems, the anatomical and biochemical pathways mediating these effects and their relation to the behavioral and pharmacological actions of the drugs. Compounds to be studied include cholinergic and anticholinergic agents and agents such as choline, deanol and physostigmine which are used to promote central cholinergic activity; hemicholinium and cyclocholine, a new compound producing acetylcholine depletion, opiates which reportedly inhibit acetylcholine release, antidepressants (amitrityline, DMI) neuroleptics (spiroperidol, chlorpromazine, clozapine) and dopaminergic agents (apomorphine, 1-DOPA, bromocriptine). The last groups will be used to investigate modulation of cholinergic activity in the corpus striatum by other neurotransmitters.